Mapping around SW London mostly. Done most of Wandsworth and Fulham with my flatmate Andy.
I do the cycle map with Andy:
http://www.opencyclemap.org/ (and also the third layer on the www.openstreetmap.org site these days)
Other stuff I'm involved in:
No names map (highlights streets with no name):
Progress images (shows regions in OSM as snapshots over time going back into the OSM dark ages):
And you can blame me for some of the relations handling code in Potlatch too!